But don't they cost an insane amount? I was quoted like $24K once for a set for a Porsche.

Indeed a company called DYMAG used to make them with full carbon fiber barrels and spokes for over 20k, but they dont make auto wheels anymore just didn't work so well. The closest there is are the carbon fiber actual applications to the wheels. Actual carbon that is applied to the aluminum to give that full Carbon appearance.

When owners of cars like the Ferrari 458, McLaren MP4-12C, and Lamborghini Aventador look to improve the style and performance of their exotic sports cars, they immediately turn to HRE Wheels. The level of quality, performance, and style of HRE’s forged wheels is unmatched. So how do you improve on the best? HRE’s answer is the new HRE Carbon Series CF2; the most exclusive performance wheels ever created.

Utilizing a full carbon-fiber rim barrel fitted to HRE’s competition-proven forged-aluminum centers, the Carbon Series CF2 is HRE’s new range-topping carbon-fiber wheel series, expected to launch in early 2013. The lightweight carbon-fiber rim barrel combined with titanium fasteners and forged centers, maximizes strength while minimizing mass and rotational inertia. Weight savings of up to 25% are expected over a typical forged aluminum wheel. The CF2 weighed in at under 16 lbs.

“As everyone knows, any HRE wheel is exclusive, but our most discerning customers have been pleading with us to go further and introduce another Carbon Series,” said HRE President, Alan Peltier. “These customers don’t care about price. They only want the coolest, most exclusive wheels they can buy and from a brand they can trust, hence the creation of the Carbon Series CF2.”

HRE introduced its first Carbon Series of wheels in 2009 and has been working to create this 2nd generation of carbon-fiber wheels with eventual TUV certification in mind; coordinating with TUV to create carbon-specific standards that go beyond normal forged aluminum requirements to ensure that these won’t be just the sexiest wheels you can buy, but also wheels you know you can trust, from the brand you can trust.

Indeed a company called DYMAG used to make them with full carbon fiber barrels and spokes for over 20k, but they dont make auto wheels anymore just didn't work so well. The closest there is are the carbon fiber actual applications to the wheels. Actual carbon that is applied to the aluminum to give that full Carbon appearance.

The 2013 Agera R features the world’s first hollow, one piece, super light carbon fiber wheel, using a proprietary method developed by Koenigsegg named Aircore™ Technology. The Aircore™ wheels save close to 20kg in unsprung mass, while providing great integrity and safety. The only metal part in the wheel is the tire valve – the rest is all once piece hollow carbon.